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EGLE's 'rock librarian' explains what's involved in identifying mystery mineral in the Upper Peninsula

Mystery mineral in the Upper PeninsulaWhen Adventure Mining Company, a mine tour company in the Upper Peninsula town of Greenland, Mich., had recently pumped water out of the mine's subterranean third level, they spotted a bright blue mysterious mineral. It got the attention of MLive which featured a story about it, and the story quickly spread internationally. Commenters on social media offered their guesses as to what it may be.

It's unclear if the company is pursuing identification of the mystery material, but Melanie Humphrey, geologist at the Michigan Department of Environment, Great Lakes, and Energy's (EGLE) Upper Peninsula Geological Repository, known as a rock library, says said there are a number of methods that can be used to get clues.

Most common minerals can be identified by their basic physical properties in the field, such as:

  • Color (also color of a "streak" if it can be made by swiping the specimen on a piece of porcelain, creating a powder).
  • Shape/structure (crystal form or amorphous?).
  • How it breaks apart (cleavage or fracture).
  • Density/specific gravity (can get an idea by "hefting" to see if it's heavy for its size),
  • Luster (shiny, dull, glassy).
  • Checking for magnetism.
  • Fluorescence (like the recent "Yooperlite" ® phenomenon).
  • Radioactivity.
  • Smell (yes, some minerals have a distinct smell), and
  • Taste (not recommended to perform this test due to safety concerns)

Another field test that can identify certain chemical composition of a mineral or rock is testing with a dilute acid to see if it reacts (fizzes).

"Identifying physical properties can give clues about the chemical composition of a mineral," Humphrey noted. "However, a trip to the lab to perform analytical techniques that will provide the specific chemical makeup affords assurance of the identification of a mineral and is the only way to confirm discovery of a new one."

So far, the mineral has not been positively identified, although the mine company says it is a "secondary mineral that is caused by a reaction with air and water." Humphrey speculates it may be azurite, as it is associated with copper ores and can occur as bright blue. However, she cautions that color alone is not conclusive for identification.

Have a rock that mystifies you? Contact Humphrey at:

Caption: Mystery mineral from mine in Greenland, Mich. Credit: Adventure Mining Company.

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